Xyalidae Chitwood, 1951
|Pseudosteineria sp (Xyalidae): Cephalic
(from Cesaroni et al., 2017)
- A widespread family of mostly
marine free-living nematodes.
- Free-living nematodes of marine and brackish
water; often among the most abundant of the nematode taxa in an
- Body length 0.5-2 mm.
- Cuticle finely striated and with
long somatic setae.
- Ocelli sometimes present.
- Mouth cavity simple, funnel-shaped, denticles either
absent or minute.
- 6+4 sensillae
almost always situated very close, for example, the 2nd annule with 6 cephalic setae
anf the third with 4. There may be with additional cephalic setae.
- Esophagus cylindrical.
- Female monodelphic prodelphic, vulva at
60-65% of body length. Per Lorenzen (1994, in didelphic forms, the
anterior gonad is always on the left of the intestine and the posterior
gonad on the right.
- Male with two
testes, occur commonly.
some marine forms with spiral amphids.
- Tail elongate conoid, terminated in a short spinneret..
- Many of the species descriptions of nematodes made in the
20th century were made basaed on very few specimens with relatively few
characters of taxonomic value (Venekey et al., 2014). Consequently,
taxonomic reviews and revisions are difficult,
Cesaroni, L. Guidi, L., Balsamo, M., Semprucci, F.
2017. Scanning electron microscopy in the taxonomical study of free-living
marine nematodes. Microscopie 28:6970
Fonseca, G., Bezerra, T.M. 2014. 7.14 Order Monhysterida in A.
Schmidt-Rhaesa. Handbook of Zoology, Gastrotricha, Cycloneuralia and Gnathifers,
Vol 2. Nematoda. De Gruyter, Berlin. 759p
Lorenzen S (1994) The phylogenetic systematics of free-living nematodes.The
Ray Society Institute, London, n.162
Venekey, V., Gheller, P.F., Maria , T.F., Brustolin, M.C., Kandratavicius ,
N., Vieira , D.C., Brito, S., Souza, G.S., Fonseca, G. The state of the art of
Xyalidae (Nematoda, Monhysterida) with reference to the Brazilian records.
Marine Biodiversity DOI 10.1007/s12526-014-0226-3
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